Exogenous addition of nitrate nitrogen regulates the uptake and translocation of lead (Pb) by Iris lacteal Pall. var. chinensis (Fisch.) Koidz.

Since Pb is a non-biodegradable inorganic pollutant and a non-essential metal,its long-term presence in soil poses a great threat to the environment.Iris lactea Pall.var.chinensis(Fisch.)Koidz.,a perennial dense bush herb with high resistance of Pb and wide adaptability,was used in pot experiments to study the effects of exogenous nitrate N(NO_(3)^(–)-N)on the absorption and transportation of Pb and plant growth under different Pb concentrations.Then,the mechanism of NO_(3)^(-)-N affecting Pb and nutrient uptake and transport was explored.The concentration of Pb in the experiment ranged from 0 to 1600 mg/kg,and the added concentration of NO_(3)^(-)-N was 0.0–0.3 g/kg.The results showed that I.lactea was highly tolerant to Pb,and the shoot fraction was more sensitive to varied Pb concentrations in the soil than the root fraction.This protective function became more pronounced under the condition of raised Pb concentration in the soil.When the concentration of Pb in the soil reached 800 mg/kg,the highest Pb content of I.lactea was found under the condition of 0.1 g/kg of NO–3-N addition.When Pb concentration in the soil increased to 1600 mg/kg,the increase in NO_(3)^(-)-N addition promoted Pb uptake by the root.To ensure the well growth of I.lactea and the effect of remediation of Pb-contaminated soil,the recommended concentration of NO–3-N in the soil is 0.1 g/kg.This result provides a theoretical basis for exogenous N regulation of phytoremediation of Pb-contaminated soil.

Nitrate Nitrogen Content Characteristics in Groundwater of Typical Planting Areas in Liao River Basin

The contents of nitrate nitrogen（NO-3-N） in underground water from typical planting areas in Liao river basin were analyzed, so as to provide theoretical basis for rational fertilization and effectively prevent the NO-3-N content from exceeding standard. The results showed that difference of the contents of NO-3-N in groundwater from different typical planting areas was significant. The highest content of NO-3-N in underground water was 37.4 mg/L from flower-growing region, then 22. 3 mg/L from maize-growing region, 21.9 mg/L from vegetable-growing region, and the lowest content of NO-3-N in underground water was 19.2 mg/L from rice-growing region. Except rice-growing region, the contents of NO-3-N in underground water of the samples in all planting areas were exceeding standard limit; potential health risk still existed in rice-growing region. Accordingly 12.5%-87.5%, 9.4%-75.5%, 17.9%-58.9% and 21.4%-96.0% of the samples were exceeding standard limit in maize growing region, rice-growing region, vegetable-growing region and flower-growing region. The contents of NO-3-N in under-groundwater before the rainy season was higher than that of NO-3-N in under-groundwater after the rainy season at the same depth of the well.

Effects of Soil Nitrate Nitrogen Residues and Leaching for Different Kinds of Slow-release Nitrogen Fertilizers in Tall-fescue Soil

ObjectiveThe aim was to explore the movement of nitrate nitrogen in tall-fescue soils by different kinds of slow release nitrogen fertilizers. MethodBased on infiltration-tanks and test plots, a new and environment friendly fertilizer was explored. ResultThe results show that compared with urea treatment, slow-release nitrogen fertilizer treatments could reduce nitrate nitrogen content and leaching amount in soils. Compared with PCU30 and IU treatments, the PCU60 treatment became more efficient in reducing nitrate content and leaching amount in 0-90 cm soil layer. ConclusionIn summary, slow-release nitrogen fertilizer, which can reduce soil nitrate content and leaching losses, is a kind of novel fertilizer with high environmental benefit and promising application.

Moving Dynamics of Nitrate Nitrogen in Soil of Maize Field on Meadow Soil of Daling River Valley in Liaoning and Its Fertilization Controlling

The moving dynamics of nitrate nitrogen（NO3-N）in soil of maize field on meadow soil of Daling river valley in Liaoning and its rational fertilization controlling were discussed in this study by the designing of different kinds of N application methods.The results showed that the content of NO3-N in soil was increased with the amount of nitrogen fertilizer;At the same amount of nitrogen fertilizer,the content of NO3-N in soil showed a trend of chemical fertilizerstraw treatmentslow controlled release fertilizer.Based on the requirement of roots in different growth stages to nutrition,the migration directions of NO3-N could be regulated by each layer of soil.In the early growth stage,the NO3-N would move upward,while it moved downward in the late growth stage.Straw returning treatment could improve the keeping ability of soil to NO3-N and avoid the downward migration of NO3-N,as well as reduce the damage of groundwater pollution.The use of slow controlled release fertilizer had achieved the continuing releasing of nutrition.Moreover,the peak of nutrition releasing had been delayed for 30 d,which had met the requirement of nutrient supply in maturing stage.The yield of slow controlled release fertilizer treatment was the highest with the least accumulation of NO3-N and less negative influence on environment.The yield of straw returning treatment and chemical fertilizer treatment was closed to each other.

Seasonal Cycle Analysis of the Nitrate Nitrogen and Nitrite Nitrogen in the Bohai Sea

During 1985-1987, the concentration of nitrate nitrogen was higher in the Laizhou Bay and the Bohai Bay while that of nitrite nitrogen was higher in the Liaodong Bay and the Bohai Bay. The concentration of nitrate nitrogen was highest in winter and lowest in summer while that of nitrite nitrogen was highest in autumn and lowest in spring. The seasonal variation of the concentration of nitrate nitrogen was maximum in the Laizhou Bay and the Bohai Bay while that of the concentration of nitrite nitrogen was maximum in the Liaodong Bay. There was a great difference in the concentration of nitrate nitrogen between the surface and the bottom in autumn and in the concentration of nitrite nitrogen between the surface and the bottom in summer. The main reason for the seasonal variations of the concentration of nitrate nitrogen and nitrite nitrogen was the marine biochemical process. The nitrate nitrogen and nitrite nitrogen in the Bohai Sea basically maintained a quasi-equilibrium state seasonal cycle. The quasi-equilibrium state seasonal cycle of nitrate nitrogen and nitrite nitrogen at the bottom was stable while that at the surface was liable to variations caused by other factors.

Effects of autumn plowing on the movement and correlation of moisture,heat and nitrate nitrogen in seasonal freeze-thaw soil

A two-year experiment was established in northern Xinjiang to investigate the effects of autumn plowing methods on nitrate nitrogen accumulation,spring-sown soil conditions and cotton emergence rate,and to explore the response relationship between soil water,heat and nitrate nitrogen.The experiment included five autumn plowing treatments,namely,plough tillage(FG),no-tillage(MG),ridge and furrow alternation(LG),plough tillage with straw mulch(FJ)and plough tillage with activated charcoal mulch(FH).The results showed that both FH and FJ treatments were beneficial to promote the nitrate-nitrogen accumulation in topsoil,while FG,MG and LG treatments aggravated the nitrate nitrogen leaching in topsoil.During the freezing period,FH and FJ treatments were beneficial to reduce soil heat loss and facilitate the coordinated upward migration of soil water and nitrate nitrogen.In the thawing period,FH and FJ treatments favored suppressing the synergistic downward transport of soil water and nitrate-nitrogen and motivated the synergistic upward migration of heat and nitrate nitrogen in deep soil.Binary regression analysis suggested that the interaction between water,heat and nitrate nitrogen under FH and FJ treatments showed a highly significant correlation.FH and FJ treatments showed obvious advantages in regulating soil conditions and optimizing soil water,heat and nitrate nitrogen co-transport mechanism.During the spring sowing period,the FH and FJ treatments increased the average soil temperature by 0.99℃and 1.29℃,and the average soil moisture content by 6.01%and 8.70%,and the average soil nitrate content by 10.20 mg/kg and 10.47 mg/kg,in the 0-25 cm soil layer,respectively.FH and FJ treatments significantly grew the emergence rate of cotton,which can be used as the main autumn tillage strategies in arid areas of northern Xinjiang.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Nitrogen and phosphorus changes and optimal drainage time of flooded paddy field based on environmental factors

While many controlled irrigation and drainage techniques have been adopted in China, the environmental effects of these techniques require further investigation. This study was conducted to examine the changes of nitrogen and phosphorus of a flooded paddy water system after fertilizer application and at each growth stage so as to obtain the optimal drainage time at each growth stage. Four treatments with different water level management methods at each growth stage were conducted under the condition of ten-day continuous flooding. Results show that the ammonia nitrogen （ NH4-N ） concentration reached the peak value once the fertilizer was applied, and then decreased to a relatively low level seven to ten days later, and that the nitrate nitrogen （NO^-N） concentration gradually rose to its peak value, which appeared later in subsurface water than in surface water. Continuous flooding could effectively reduce the concentrations of NH^-N , NO3-N, and total phosphorus （TP） in surface water. However, the paddy water disturbance, in the process of soil surface adsorption and nitrification, caused NH]-N to be released and increased the concentrations of NH4-N and NO^-N in surface water. A multi-objective controlled drainage model based on environmental factors was established in order to obtain the optimal drainage time at each growth stage and better guide the drainage practices of farmers. The optimal times for surface drainage are the fourth, sixth, fifth, and sixth days after flooding at the tillering, jointing-booting, heading-flowering, and milking stages, respectively.

Genome-wide identification and expression analysis of NIN-like Protein(NLP)genes reveals their potential roles in the response to nitrate signaling in watermelon

To balance the relationship between high yield and low nitrogen supply,the nitrogen utilization efficiency of watermelon needs to be improved urgently.Nodule inception-like Protein(NLP)transcription factors play a key node role in nitrate response and growth and development of plant,however,comprehensive analysis of the NLP gene family in watermelon is unclear.This study explored the functional classification,evolutionary characteristics,and expression profile of the ClNLP gene family.Three ClNLPs were categorized into three groups according to their gene structure and phylogeny.All of them contained the conserved RWP-RK and PB1 domains.Evolutionary analysis of ClNLPs revealed that ClNLP1 and ClNLP3 underwent strong purified selection.In addition,cis-acting elements related to plant hormones and abiotic stresses were present in the ClNLP promoter.According to tissue-specific analysis ClNLP was widely expressed in roots,stems,leaves,flowers and fruits,and ClNLP1 was significantly induced in the roots of different nitrogen utilization varieties under different nitrate nitrogen supply.The SRTING functional protein association network suggested that ClNLP1 is associated with most genes,such as NRT1.1,NRT2.1,NIA1,and NIR1,and the dual-luciferase reporter assay found that ClNLP1 positively regulates the expression of ClNRT2.1.We speculated that ClNLP1 might play a central role in regulating the response of watermelon to nitrate nitrogen.

Identification of Differentially Expressed Genes Induced by Ammonium Nitrogen in Rice Using mRNA Differential Display

RNAs isolated from ammonium- and nitrate-treated rice leaves were used to screen differentially expressed genes through mRNA differential display. A total of 72 bands appeared significant differences and some of them were further confirmed by reverse Northern and Northern blot. The results showed that two genes, A-02 （Oryza sativa drought stress related mRNA） and A-03 （Zea mays partial mRNA for TFIIB-related protein） were highly up-regulated in the ammonium-fed rice leaves. The enzyme assays showed that the activities of the two anti-oxidative enzymes, catalase and peroxidase, and the content of a non-enzymic antioxidant, glutathione, were significantly higher in the ammonium-fed rice leaves than those in the nitrate-fed ones, indicating that the ammonium nutrition might be beneficial for rice plants to improve the stress resistance during growth and development.

The Effect of Different Nitrogen Form on Key Enzyme Activity of Sugarbeet(Vulgaris L.) Carbon and Nitrogen Metabolism

This article analyses the effect of the proportion of the different nitrogen forms on key enzyme activity of carbon and nitrogen metabolism under the condition of nutritional water while Tian Yan-7 was used as experimental material.The result showed that nitrate reductase(NR) activity in the leaves gradually enhanced with the increase of NO - 3.No matter in root or leaves,glutamina synthetase(GS) activity first enhanced with increasing NH + 4 when NH + 4 was lower than that of NO - 3,and GS activity was the highest when NH + 4and NO - 3 was equal,then GS activity declined with NH + 4 increasing further.In the anaphase of growth,synthetic activity in root of sucrose synthetase(SS) in the mixed NH + 4 and NO - 3 was obviously highr than or NO - 3 alone.Both of the root and sugar yields were the highest when the proportion of NH + 4 and NO - 3 was 1:1.

Effects of Growth Regulator MeJA on Nitrogen Metabolism in Rice under Cadmium Stress

Taking high nitrogen efficiency and low nitrogen tolerance C156 and C111 rice varieties as materials,the aboveground and underground biomass,total nitrogen uptake,nitrate nitrogen content and other indicators,the effects of methyl jasmonate(MeJA)on the growth,development and NO3^-distribution of rice under cadmium stress were studied.The results showed that under cadmium stress,more nitrate nitrogen of rice seedlings was distributed to roots,which enhanced the stress resistance of crops.The concentration of methyl jasmonate at 70μmol/L is a boundary line,and the methyl jasmonate at 70μmol/L is recommended as the later research material.Methyl jasmonate can increase the biomass and total nitrogen uptake of C156 under cadmium stress,but the effect is not significant.It can significantly improve the NUE of C111 based on biomass.

Laboratory and numerical modelling of irrigation infiltration and nitrogen leaching in homogeneous soils

Nitrogen (N) plays a key role in crop growth and production;however,data are lacking especially regarding the interaction of biochar,grass cover,and irrigation on N leaching in saturated soil profiles.Eighteen soil columns with 20-cm diameter and 60-cm height were designed to characterize the effects of different grass cover and biochar combinations,i.e.,bare soil+0%biochar (control,CK),perennial ryegrass+0%biochar (C1),Festuca arundinacea+0%biochar (C2),perennial ryegrass+1%biochar (C3),perennial ryegrass+2%biochar (C4),perennial ryegrass+3%biochar (C5),F.arundinacea+1%biochar (C6),F.arundinacea+2% biochar (C7),and F.arundinacea+3%biochar (C8),on periodic irrigation infiltration and N leaching in homogeneous loess soils from July to December 2020.Leachates in CK were 10.2%–35.3%higher than those in C1 and C2.Both perennial ryegrass and F.arundinacea decreased the volumes of leachates and delayed the leaching process in the 1%,2%,and 3%biochar treatments,and the vertical leaching rate decreased with biochar addition.The N leaching losses were concentrated in the first few leaching tests,and both total N (TN) and nitrate (NO_(3)^(-))-N concentrations in CK and C1–C8 decreased with increasing leaching test times.Biochar addition (1%,2%,and 3%) could further reduce the leaching risk of NO_(3)^(-)-N and the NO_(3)^(-)-N loss decreased with biochar addition.However,compared to 1%biochar,2% biochar promoted the leaching of TN under both grass cover types.The N leaching losses in CK,C1,C2,C3,C4,C6,and C7 were primarily in the form of NO_(3)^(-)-N.Among these treatments,CK,C1,and C2had the highest cumulative leaching fractions NO_(3)^(-)-N (>90%),followed by those in C3,C4,C6,and C7 (>80%).The cumulative leaching fraction of NO_(3)^(-)-N decreased with increasing leaching test times and biochar addition,and 3%biochar addition (i.e.,C5 and C8) reduced it to approximately 50%.The one-dimensional advective-dispersive-reactive transport equation can be used as an effective numerical approach to simulate and predict NO_(3)^(-)-N leaching in saturated homogeneous soils.Understanding the effects of different biochar and grass combinations on N leaching can help us design environmentally friendly interventions to manage irrigated farming ecosystems and reduce N leaching into groundwater.

Enzyme Activities and Microbial Communities in Subtropical Forest Soil Aggregates to Ammonium and Nitrate-Nitrogen Additions

A laboratory incubation experiment was established to examine the impacts of nitrate and ammonium nitrogen additions on soil microbial attributes of a subtropical Pinus elliottii forest ecosystem in southern China. Soils were subjected to three different treatments： the control with no nitrogen addition （CK）, the ammonium nitrogen addition （NH4^＋-N）, and the nitrate nitrogen addition （NO23^-N）. Samples from bulk and two different size fractions （macroaggregate （〉250 pm） and microaggregate （53-250 μm）） were analyzed for soil properties, enzyme activities and microbial communities on day 7 and 15 of the incubation. Our study demonstrated that NH4^＋-N had a 9rearer influence on soil microbial activities than NO3-N. NH4^＋-N additions resulted in significant increases in 13-1,4-glucosidase （βG） and β-1,4-N-acetyl glucosaminidase （NAG） enzyme activities in bulk, macroaggregate and microag- gregate soils after 7 and 15 days incubation. NO3^-N additions only significantly increased in βG and NAG enzyme activities in bulk, macroaggregate soils after 7 and 15 days incubation, but not in microaggregate. All NH4^＋-N and NO3-N additions resulted in significant increases in gram-positive bacterial PLFAs in microaggregates. Only a significant correlation between soil nutrient contents and enzyme activities in macroaggregates was founded, which suggests that the soil aggregation structure played an important role in the determining enzyme activities.

Rice Grain Chalkiness Is Negatively Correlated with Root Activity During Grain Filling

Field and pot experiments were conducted using indica rice varieties with differential chalkiness. There were significant differences in root activity among the varieties. The percentages of chalky grains and chalky area were both negatively correlated with root activity expressed as α-naphthylamine oxidation ability （RA） per gram of fresh root （RAfw） , RA per spikelet （RAgrn）, or RA per sink capacity （RAsink）. The RAsink was more closely related to chalkiness than RAt, and RAgrn when varieties differed greatly in panicle size and grain weight. Application of NO3^--N fertilizer at heading resulted in higher root activity and reduced chalkiness. Application of 30 mg/L NaN3 （respiration inhibitor） resulted in reduced root activity and increased chalkiness for one variety ＇GD9501＇, but for the other variety ＇Qinluai＇ was in reverse. The percentages of chalky grains and chalky area were negatively correlated with root activity at 10 days after heading under different chemical treatments （r=-0.8567^＊ and r=-0.9211^＊＊, respectively）.

A putative 6-transmembrane nitrate transporter OsNRT1.1b plays a key role in rice under low nitrogen

OsNRT1.1a is a low-affinity nitrate（NO_3^-） transporter gene. In this study, another mRNA splicing product, OsNRT1.1b,putatively encoding a protein with six transmembrane domains, was identified based on the rice genomic database and bioinformatics analysis. OsNRT1.1a/OsNRT1.1b expression in Xenopus oocytes showed OsNRT1.1a-expressing oocytes accumulated ^（15）N levels to about half as compared to OsNRT1.1bexpressing oocytes. The electrophysiological recording of OsNRT1.1b-expressing oocytes treated with 0.25 mM NO_3^- confirmed ^（15）N accumulation data. More functional assays were performed to examine the function of OsNRT1.1b in rice. The expression of both OsNRT1.1a and OsNRT1.1b was abundant in roots and downregulated by nitrogen（N） deficiency. The shoot biomass of transgenic rice plants with OsNRT1.1a or OsNRT1.1b overexpression increased under various N supplies under hydroponic conditions compared to wild-type（WT）. The OsNRT1.1a overexpression lines showed increased plant N accumulation compared to the WT in 1.25 mM NH_4NO_3 and 2.5 mM NO_3^- or NH_4~＋ treatments, but not in 0.125 mM NH_4NO_3.However, OsNRT1.1b overexpression lines increased total N accumulation in all N treatments, including 0.125 m M NH_4NO_3,suggesting that under low N condition, OsNRT1.1b would accumulate more N in plants and improve rice growth, but also that OsNRT1.1a had no such function in rice plants.

Experimental Study on the Distribution of Soil Nitrate and Ammonium Nitrogen under Controlled Drainage

A field experimental project was set up to assess the effects of controlled drainage on the distribution and concentration of nitrogen in the soil at the Irrigation and Drainage Experimental Station under Four-Lake Engineering Administration of Jingzhou City, Hubei Province. Two plots drain runoff by controlled drainage system, with an area of 0.1 hm^2 （20 m×50 m） each. The third one with an area of 0.04 hm^2 （8 m×50 m） has a conventional subsurface drainage system. Under this experimental condition, the study draws the following conclusions： ① The controlled drainage system has a remarkable effect on the diminishing ratios of nitrate nitrogen between neighboring layers. It is presented that the diminishing ratio increases with the raising height of drain outlet. Controlled drainage system also reduces the transference of nitrate nitrogen in topsoil.② Different from nitrate nitrogen, the concentration of ammonium nitrogen is stable along the longitudinal section of soil, which is little affected by the controlled drainage system. It indicates that the concentration of ammonium nitrogen decreases according to the lowering of controlling height of the drain outlet.

Soil acidification of alfisols influenced by nitrate and ammonium nitrogen level in tea plantation

Nitrogen is an important fertilizer in tea production,but it is also an important factor in tea garden soil acidification.The relationship between absorption and transport of different forms of nitrogen in the tea plant and soil acidification is still unknown.In order to explore the different characteristics of absorption,utilization and distribution of nitrogen,stable isotope 15N tracer technique was used to measure the absorption,utilization and allocation of nitrate nitrogen(NO_(3-)15N)and ammonium nitrogen(NH4-15N)under the same nitrogen application amount of tea tree seedlings as experimental materials.The results showed that the tea seedlings had the same pattern of nitrogen application:tissue nitrogen content increased after fertilization,remarkable rising at 7 d and the absorption speed increased quickly after 28 d,finally reached its maximum at 56 d.The nitrogen use efficiency of two nitrogen sources in two kinds of soil varied not significantly.The maximum NUE of NO_(3-)^(15)N reached 12.66%,and at the same time NH_(4)-^(15)N utilization rose up to 11.54%.According to the absorption of soil nitrogen and nitrogen fertilizer in the two kinds of soil,it is concluded that the soil nitrogen cannot meet the growth needs of tea tree and extra nitrogen supply was required.The declined soil pH indicated that fertilizer should be used in moderation,which can not only satisfy the growth of tea tree but also to restrict soil acidification.

Effects of Aeration on Nitrification Process in a Polluted Urban River

[Objective] The study aimed to discuss the effects of aeration on nitrification process in a polluted urban river, [Metbod] Through indoor simulation experiments, the effects of different aeration conditions （aerating water named Ew, aerating sediment named Es ） on nitrification process in a polluted urban river were studied.[ Result]The nitrification of the control group named Ec proceeded slowly, while two kinds of aeration promo- ted the process of nitrification, that is, the peak values of nitrate nitrogen of Ew and Es group were respectively 5.15 and 3.83 times that of Ec group. During aeration, NO2 --N accumulation in the overlying water of Ew and Es group lasted for 10 and 14 days separately, and the maximum concentrations reached 11.41 and 7.41 mg/L respectively. Nitrification process was not consistent during the two aeration conditions, that is, the rate of nitrite oxidation in Ew group was faster than that in Es group. Denitrification process was significant after aeration, and the concentration of nitrate nitrogen in Ew and Es group was 1.26 and 2.82 mg/L respectively at the end of the experiment. [ Conclusion]The research could provide scientific references for the restoration of polluted urban rivers.

The Growth Effect of Enhanced Ammonium Nutrition on Maize

The two maize varieties,Yuanzheng 808(astrictive type) and Sidan 19(explanate type),were cultured in pots.There were six treatments which the proportion of NO 3 - N and NH 4 + N were 1∶0 (treatment 1),2∶1(treatment 2),1∶1(treatment 3),1∶2(treatment 4),0∶1(treatment 5) and CK(no nitrogen) respectively.After emergence of seedings,the samples were picked up per 20 days in the growth period and measured chlorophyll contents,nitrate reductase(NR) activity,the weight of dry matter and single plant seed yield respectively.The result showed that enhanced ammonium nutrition (EAN) may increase chlorophyll content,dry matter weight and single plant seed yield.But there was a difference between varieties.To Yuanzheng 808,treatment 2 was the highest yield in all treatments;but treatment 4 was the highest yield to Sidan 19.